Stable, fluid, soap thickened oil lubricant compositions



United States Patent 3,383,312 STABLE, FLUKE), 501ml Ti-lliCliliNED GELLUBRKQANT CGMIPUSETEGNS Walter J. Coppock, Wallingford, Pa, assignor toSun itljtil Company, Philadelphia, Pa, a corporation of New ersey NoDrawing. Filed Dec. 21, N64, Ser, No. 420,0d2 8 Claims. (til. 252-36) Inone aspect this invention is a method of preparing fluid, soap thickenedoil lubricants which are stable in that there is no tendency of the soapto separate from the oil during storage or use. Stability is achieved byincorporating a small amount of a cyclic aluminum oxide trimer into thelubricant. In another aspect the invention is stable, fluid, soapthickened oil lubricants comprising lubricating oil, soap, and theaforesaid trimer.

Fluid lubricant compositions comprising a major amount of lubricatingoil and 0.l2.5% soap dispersed therein are known. The compositions arefluid, i.e., pourable, as opposed to being grease, i.e., semisolid,compositions. The purpose of the soap is to increase the apparentviscosity of the oil and the composition is used, for example, inlubricating exposed gear teeth or exposed bearings, i.e., surfaces wherein the absence of the soap the oil would tend to drip off or otherwiseescape from the surface to be lubricated. A number of other applicationsof soap thickened oil fluid lubricants are also known; see, e.g., U.S.Patent 3,071,547.

In most soap thickened oil fluid lubricants the oil is a minerallubricating oil and the soap is a metal salt of a fatty acid. Althoughsuch lubricants have a number of desirable properties they have anundesirable characteristic in that the soap tends to settle out of theoil. For example, if a drum of a homogeneous fluid lithium stearatethickened oil is stored for six months and the contents then examined,it will often be found that the material at the bottom of the drum ismainly oil and the material at the top of the drum is mainly soap. Thisstorage instability is an obvious disadvantage and a means of preventingsame is desired.

It has now been found that fluid lubricants comprising minerallubricating oils thickened with metal soaps of fatty acids can bestabilized against separation of the soap by the incorporation thereinof a small amount of a cyclic aluminum oxide trimer having certaincharacteristics more fully defined hereinafter. In one aspect theinvention is fluid, stable, oil-soap-trimer compositions. In anotheraspect it is a method of preparing same.

It is recognized that in fluid, soap thickened oil lubricants, as ingreases, the soap is not dissolved, at least at room temperature, in theoil (except for possibly an insignificant amount) but rather isdispersed therein. Consequently when it is stated herein that the soapseparates from the oil it is obviously not meant that the soap comes outof the solution. What is meant is that the dispersed soap settles sothat What was initially a homogeneous dispersion becomes non-homogeneousor, in extreme cases, two distinct layers, a soap layer and an oillayer.

The oil component of the compositions of the invention is a minerallubricating oil. Being a mineral oil it will also be a hydrocarbon oil.Any particular type of mineral oil is suitable so long as it haslubricating properties. Thus the oil can be paraffinic, naphthenic, etc.It can be a straight distillate oil, a solvent refined oil, etc. Theviscosity of the oil will vary depending upon the intended applicationbut will usually be 83-3500 S.U.S. at 100 F., more frequently 1003000S.U.S. at 100 F. The VI of the oil Will depend upon the type of oil andits method of preparation but will usually be 0400. The amount of oil inthe compositions of the invention will be 9599.8% based on the totalcomposition, i.e., on the oil, soap, and

trimer. All percentages and parts herein are by weight.

T he soap component of the compositions of the invention is a fatty acidmetal soap. The fatty acid should contain 1222 carbon atoms and ispreferably an unsubstituted fatty acid such as stearic, palmitic, etc.but it can also be a substituted fatty acid such as IZ-hydroxy stearicacid. The preferred fatty acid is stearic acid. The metal component ofthe soap can be any of the conventional soap forming metals such assodium, lithium, barium, calcium, aluminum, etc. The tendency of thesoap to separate from a fluid mineral oil lubricant is not dependentupon the specific metal present in the soap. For economic reasons thealkali and alkaline earth metals are preferred for the present purpose.Of these the alkali metals are preferred, especially lithium since oilsthickened with lithium soaps have good resistance to water and hightemperatures.

The amount of soap used in the compositions will depend upon theintended application thereof but will usually be 0.l2.5% based on thetotal composition. In any event the amount of soap will be sufiicient toincrease the apparent viscosity of the oil. The viscosity is referred toas apparent because although addition of the soap to the oil increasesthe viscosity of the oil as determined by conventional analyticalmethods, when the soap thickened oil is subjected to shear its viscosityreduces to that of the oil alone. In other words, the soap thickened oilis a non- Newtonian fluid. The amount of soap will normally be such thatthe final fluid oil-soap-trimcr composition has a MacMichael viscosityat 70 F. (oil cup) of 225, the MacMichael viscosity being used insteadof S.U.S. viscosity because S.U.S. viscosities on dispersions are notreliable. The maximum amount of soap is limited to 2.5% because abovethis amount the soap thickened oil is usually of grease consistencyrather than being fluid. The present invention does not 'mclude greasecomposi tions because with these there is no soap separation problem. Inother words, in an oil thickened to grease consistency with a fatty acidmetal soap there is no problem of the soap settling out. This problemdoes exist, however, in a fluid soap thickened oil. The preferred amountof soap for the present purpose is 0.51.5%.

The substituted cyclic aluminum oxide trimer which is included in thecompositions of the invention in order to prevent separation of the soapfrom the oil has the structure wherein R in at least one instance is anacylate anion '(RCOO) of an aliphatic monoearboxylic acid containingl222 carbon atoms and in any remaining instances is an alkoxy anion (RO)of an alcohol containing 1-46 carbon atoms such as ethanol, hexanol,octanol, isopropanol, heptanol, sec-butanol, etc. Preferably the alcoholfrom which the alkoxy anion is derived contains 2-5 carbon atoms andmore preferably is isopropanol. Examples of suitable acids from whichthe acylate anion is derived are stearic acid, palmitic acid, IZ-hydroxystearic, etc. lt is not necessary that the acid from which the acylateanions in the trimer are derived be the same as the acid used to formthe soap which is present in the compositions of the invention.Furthermore, it is not necessary that all acylate anions in the trimerbe the same or that all alkoxy anions in the trimer be the same.Although it is sufficient if only one R in (1) above is an acylate anionof the type described preferably at least 2 Rs, more preferably all Rs,are acylate anions.

The substituted cyclic aluminum oxide trimer and the method of makingsame are described in detail in US. Patent No. 2,979,497, issued toJacobus Rinse. As described in this patent, an aliphatic monocarboxylicacid, an aluminum alkoxide, and water are mixed and then held at atemperature of l76-248 F. until formation and liberation of alcoholceases, after which the temperature is raised to and maintained at about356 F. until further formation and liberation of alcohol ceases. Theproduct is the substituted cyclic aluminum oxide trimer. Thesubstitutions will be either acylate or alkoxy anions depending upon themole ratios of the reactants used. For example, if the mole ratio ofacid to aluminum alkoxide to water is 111:1, the product will be atriacylate cyclic aluminum oxide trimer,

(acyilate) i (acoylate)-Al Al- (acylate) If the mole ratio of acid toaluminum alkoxide to water is 2:3:3, the product will be a diacylatealkoxy cyclic aluminum oxide trimer,

(acyltlito) Al t 3 (alkoxy) -Al Al-(acylatc) Further variations in moleratios of the ingredients result in further variations of thesubstitutions on the cyclic aluminum oxide trimer.

The amount of the substituted cyclic aluminum oxide trimer, hereinreferred to as the trimer, should be in the range of 0.1-2.5% based onthe total composition since amounts within this range are effective toprevent separation of the soap from the oil. Preferably the amount usedis 054.5%. As a general rule the amount of trimer required to preventseparation of the soap decreases as the amount of soap decreases.

The trimer must be incorporated into the compositions of the inventionin a certain manner if the stabilizing effect of the trimer is to berealized. The trimer can be satisfactorily incorporated at any timeduring the preparation of the soap thickened oil or at any timethereafter so long as the composition is heated to at least 200 F.,preferably at least 300 F., after the addition of the trimer thereto.Thus if the trimer is merely added to and mixed with a fluid, soapthickened oil at room temperature the soap in the resulting threecomponent composition will still settle out during storage. If, however,the resulting three component composition is heated to at least 200 F.and then cooled to room temperature separation of the soap thereafterwill not occur. The reason why the composition containing the trimmermust reach a temperature of at least 200 F. to be stable is not knownbut such has nevertheless been found to be the case. It is apparentlynot necessary that the composition be held at a temperature of at least200 F. for any certain prescribed period because it has been found thatmerely heating to, say, 210 F. and then immediately cooling to roomtemperature is sufiicient. In any event, in a commercial operation thecomposition would usually be above 200 F. for 510 minutes because of thecharacteristics of the equipment utilized and this is the preferredprocedure.

In actual practice it will usually be much more convenient toincorporate the trimer during the preparation of the soap thickened oilcomposition. Soap thickened oils are conventionally prepared by mixingthe soap with a minor proportion, usually /t- /2, of the total oil atabout room temperature. Only a minor amount of the oil is used in orderto minimize the oil decoloration which occurs because of the subsequentheating. The soap-oil mixture is then heated with agitation to effectdissolution of the soap in the oil and the mixture is then cooled withagitation while adding the remainder of the oil thereto. During thecooling the solubility of the soap in the oil decreases and most of thesoap comes out of the oil. Normally all the remaining oil is addedbefore a temperature of 180 F. in the cooling step is reached. If anyadditives such as oxidation inhibitors are to be included in thecomposition they are normally added at about 180-200 F. After allingredients are present cooling continues until a temperature below 100R, usually room temperature, is reached.

The soap-oil mixture is normally agitated during the entire coolingcycle, i.e., even after all the oil is in and a uniform soap-oil mixtureachieved. This is done in order to prevent any gelation which mightotherwise occur. Agitation beyond that required to make a homogeneoussoap-oil mixture is not essential, however, for even if any gelationoccurs the gel can be broken up and a fluid lubricant obtained by merelyagitating the soap-oil mixture.

The soap component can be preformed or can be formed in situ in the oil.For example, stearic acid and lime can be mixed with a minor proportionof the oil. During the subsequent heating the lime and acid react toform calcium stearate and water, the latter being evaporated during theheating step.

The temperature to which the soap-oil mixture must be heated to dissolvethe soap in the oil in a reasonable length of time will vary dependingmainly upon the metal component of the soap. For alkaline earth metals atemperature of Q50350 F. is usually sufficient. With lithium soaps atemperature of 350425 F is preferred but with other alkali metal soapslower temperatures of 300400 F. are satisfactory. In any eventdissolution of the soap in the oil can be readily determined visually.

One convenient method of incorporating the trimer is to add the trimerto the oil at the same time the soap is added. The trimers suitable forthe present purpose are oily liquids completely miscible with minerallubricating oils. Since the resulting mixture will always be heated toabove 200 F. to dissolve the soap in the oil this heating willsimultaneously realize the stabilizing effect of the trimer.Alternatively, the trimer can be added at any time during the heating orcooling operations so long as a temperature of at least 200 F.,preferably at least 300 F., is reached after addition of the trimmer.

One precaution should be observed in adding the trimer when the soap isformed in situ in the oil because of the fact that this in situtechnique results in the formation of water. At high, e.g., 1015%concentrations of trimer in oil the presence of water sometimes tends toconvert the oil to grease. Furthermore this grease usually cannot beconverted to a fluid lubricant by merely agitating the grease because ofthe relatively large amount of soap present. Thus this situation is notthe same as the case men tioned previously in which gelation of the oiloccurs during the cooling cycle due to lack of agitation. Since only aminor proportion of the oil, usually Mt- /z, is normally presentinitially, the concentration of trimer will be substantially higherinitially than in the final composition. In order to avoid convertingthe oil to a grease the trimer should not be added to the oil until anywater present is removed. This presents no serious obstacle because theoil will of course be dehydrated during the heating step. If the soap ispreformed this problem of course does not arise.

The following examples illustrate the invention more specifically.

EXAMPLE '1 35.0 parts of a paraffinic solvent refined distillate oilhaving a viscosity of 100 S.U.S. at 100 F. and a VI of is charged to ajacketed vessel equipped with a paddle type agitator. Steam or coldwater can be supplied to the jacket for heating or cooling of thecontents of the vessel.

With the agitator runing and the oil at 75 iF. 0.7 art lithium stearateis added to the oil and the resulting mixture is heated over a period of2 hours to 400 F. at which temperature the lithium stearate is dissolvedin the oil. When the temperature reaches 400" F. the steam is shut 01fand the cooling water turned on. Just after cooling begins 63.9additional parts of oil is charged to the vessel and the contents of thetank are cooled to 75 \F. over a period of 2 hours. At 180 F. in thecooling step 0.4 part of dibutyl-parawreso], an oxidation inhibitor, ischarged to the vessel. The agitator is running during the entire coolingstep.

A conventional 55 gallon drum containing sample taps at the bottom, '17inches up from the bottom (hereinafter the middle), and 34 inches upfrom the bottom (hereinafter the top), is filled to a depth of 35 incheswith the oil prepared as described above. Immediately after \filling asmall sample is withdrawn from each of the sample taps and the viscosityof each sample is determined. Each sample has a MacMichael viscosity at70 F. of 1-3. The drum is then closed and is placed in storage at 75After 2 months storage another sample is withdrawn from each tap and theviscosity of each sample is determined. The results are as follows.

It is evident from this data that the soap thickened oil has poorstorage stability.

EXAMPLE 2 A soap thickened oil is prepared by the procedure of Example 1except that instead of using 35 parts oil 34.5 parts are used and 0.5part cyclic aluminum oxide trimer is added to the oil simultaneouslywith the lithium s'tearate soap. The trimer has the structure of (1)supra wherein 2 Rs are steara-te and 1 R is isopropoxy. In other wordsthe trimer is a distearate is-opropoxy cyclic aluminum oxide trimer.

The soap thickened oil prepared in this manner is charged to a 55 gallondrum similar to that used in Example 1 and tested in the same manner asin Example 1. The results are as follows: Immediately after filling thedrum each sample has a MacMichael viscosity at 70 F. of 13. After 2months storage the three samples have viscosities as follows.

MacMichael Location: viscosity at 77 F. 'Iop 13 Middle '13 Bottom 13cyclic aluminum oxide trimer having the structure R-lil lil-R wherein Rin at least one instance is an acylate anion of an aliphaticmonocarboxylic acid containing 12-22 carbon atoms and in any remaininginstances is an alkoxy anion of an alcohol containing 1-10 carbon atoms,the amount and percentages being by weight of the total composition.

2. The composition according to claim 1 wherein all Rs are acylateanions.

3. The composition according to claim 1 wherein the amount of said soapis 0.5-1.5 and the amount of said trimer is 0.5-1.5

4. The composition according to claim 1 wherein said metal is lithium.

5. A method of preparing a fluid, soap thickened mineral oil lubricantcomposition which is stable in that the tendency of the soap to separatefrom the oil is reduced which comprises forming a mixture of a minorproportion of the oil in said composition, a fatty acid metal soap inthe amount of 0.12.5% based on said composition, said amount beingsuflicient to increase the apparent viscosity of the oil in saidcomposition, heating said mixture to dissolve the soap in oil, coolingsaid mixture to below F. while adding additional oil thereto during atleast a portion of said cooling, and adding to said mixture astabilizing amount, in the range of 0.12.5%, based on said composition,of a cyclic aluminum oxide trimer having the structure wherein R in atleast one instance is an acylate anion of an aliphatic monocarboxylicacid containing 12-22 carbon atoms and in any remaining instances is analkoxy anion of an alcohol containing l-10 carbon atoms, said addingbeing at a time in the formiug-heating-cooling operation such that theresulting oil-soap-trimer mixture reaches a temperature of at least 200F.

6. The method according to claim 5 wherein all Rs are acylate anions.

7. The method according to claim 5 wherein said metal is lithium.

8. The method according to claim 5 wherein said oilsoap-trimer mixturereaches a temperature of at least 300 F.

References Cited UNITED STATES PATENTS 2,489,300 11/1949 Leyda 252-362,744,074 5/ 1956 Theobald 260-2 2,859,181 11/1958 Jordan et al. 252362,883,341 4/1959 Allison 25236 2,913,409 11/1959 Remes et al. 252-282,979,497 4/1961 Rinse 26097.5 3,055,828 9/1962 Wiley 252-35 3,216,93511/1965 Morway et al 252-39 3,231,495 1/1966 Morway et al. 252-39 DANIELE. WY MAN, Primary Examiner. I. VAUGHN, Assistant Examiner.

1. A STABLE, FLUID, SOAP THICKENED OIL LUBRICANT COMPOSITION COMPRISINGA MAJOR AMOUNT OF MINERAL LUBRICATING OIL, 0.1-2.5%, SUFFICIENT TOINCREASE THE APPARENT VISCOSITY OF SAID OIL, OF A FATTY ACID METAL SOAPDISPERSED IN SAID OIL, AND 0.1-2.5%, SUFFICIENT TO REDUCE THE TENDENCYOF SAID SOAP TO SEPARATE FROM SAID OIL, OF A SUBSTITUTED CYCLIC ALUMINUMOXIDE TRIMER HAVING THE STRUCTURE
 4. THE COMPOSITION ACCORDING TO CLAIM1 WHEREIN SAID METAL IS LITHIUM.